根尖分生区的微环境（stem cell niche）对维持根尖干细胞的活力，保证根系正常持续生长起着重要作用。目前已经报道了一些在根尖干细胞维持方面的研究，但根尖干细胞命运决定以及微环境的活力维持还没有完全阐述清楚。 

　　李霞课题组通过正向遗传学的方法，从拟南芥突T-DNA变体库中筛选根尖分生区变化的突变体，获得了一个影响根尖分生区微环境的突变体prl1，基因克隆以及互补试验证明，T-DNA插入到PRL1基因中导致突变体分生区变短以及根尖分生区微环境的组织紊乱。在拟南芥中，PRL1基因编码含有WD40重复序列的蛋白，是一个剪切复合体的组成单元，目前已有的研究表明PRL1蛋白在多种胁迫，激素和发育信号中起着作用。在我们的研究中，我们证明了PRL1参与控制根尖分生区大小以及维持根尖干细胞微环境的作用。PRL1基因在根尖分生区表达水平最高，缺失PRL1基因导致根尖静止中心细胞的紊乱排列，根尖干细胞的提前分化，以及细胞分裂活性的阻滞。遗传试验证明PRL1对限制WOX5在根尖静止中心的表达必不可少，并且PRL1作为PLETHORA (PLT1/PLT2)的上游调控发挥作用，这些结果证明PRL1在根尖分生区微环境维持和干细胞活力中起着重要作用。  

　　该结果已经在线发表在

The Plant Journal 期刊上（http://onlinelibrary.wiley.com/doi/10.1111/tpj.12733/abstract），李霞课题组的工作人员纪洪涛为本文第一作者，该工作得到973项目和国家自然科学基金项目支持。 

 　  Abstract 

　　The stem cell niche in the root meristem maintains pluripotent stem cells to ensure a constant supply of cells for root growth. Despite extensive progress, the molecular mechanisms through which root stem cell fates and stem cell niche activity are determined remain largely unknown. In Arabidopsis thaliana, the Pleiotropic Regulatory Locus 1 (PRL1) encodes a WD40-repeat protein subunit of the spliceosome-activating Nineteen complex (NTC) that plays a role in multiple stress, hormone and developmental signaling pathways. Here, we show that PRL1 is involved in the control of root meristem size and root stem cell niche activity. PRL1 is strongly expressed in the root meristem and its loss of function mutation results in disorganization of the quiescent center (QC), premature stem cell differentiation, aberrant cell division, and reduced root meristem size. Our genetic studies indicate that PRL1 is required for confined expression of the homeodomain transcription factor WOX5 in the QC and acts upstream of the transcription factor PLETHORA (PLT) in modulating stem cell niche activity and root meristem size. These findings define a role for PRL1 as an important determinant of PLT signaling that modulates maintenance of the stem cell niche and root meristem size.